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A humid atmospheric pressure plasma jet was used to treat an aqueous liquid. The transport of hydrogen peroxide and hydroxyl from the plasma to the liquid was analyzed. Two in situ liquid diagnostics for each species were compared and validated. In the case of H2O2, a spectrophotometric approach using ammonium metavanadate and electrochemical sensing based on Prussian blue carbon paste electrodes was applied. Both methods show very good agreement in trends and absolute values. The detection of OH was performed by terephthalic acid (TA) dosimetry and its distribution was visualized by the chemiluminescence of luminol. There, the measurement using TA resembles the luminol measurements and vice versa, and a very good agreement between both methods was found. [ABSTRACT FROM AUTHOR]

Bacillus spp., a class of aerobic bacteria, is widely used as a biocontrol microbe in the world. However, the reactive oxygen species (ROS) will accumulate once the aerobic bacteria are exposed to environmental stresses, which can decrease cell activity or lead to cell death. Hydroxyl radical (·OH), the strongest oxide in the ROS, can damage DNA directly, which is generated through Fenton Reaction by H2O2 and free iron. Here, we proved that the synthesis of pulcherriminic acid (PA), an iron chelator produced by Bacillus spp., could reduce DNA damage to protect cells from oxidative stress by sequestrating excess free iron, which enhanced the cell survival rates in stressful conditions (salt, antibiotic, and high temperature). It was worth noting that the synthesis of PA was found to be increased under oxidative stress. Thus, we demonstrated that the YvmB, a direct negative regulator of PA synthesis cluster yvmC-cypX, could be oxidized at cysteine residue (C57) to form a dimer losing the DNA-binding activity, which led to an improvement in PA production. Collectively, our findings highlight that YvmB senses ROS to regulate PA synthesis is one of the evolved proactive defense systems in bacteria against adverse environments. [ABSTRACT FROM AUTHOR]

Surface processes such as coatings, corrosion, photocatalysis, and tribology are greatly diversified by acid–base interactions at the surface overlayer. This study focuses on the action of a metallic copper surface as an electron donor/acceptor related to the inactivation of viruses. It was found that regarding Cu2O or Cu materials, electrostatic interaction plays a major role in virus inactivation. We applied the TPPE method to clarify the mechanism of electron transfer (ET) occurring at light-irradiated copper surfaces. The TPPE characteristics were strongly influenced by the environments, which correspond to the temperature and environment dependence of the total count of emitted electrons in the incident light wavelength scan (PE total count, NT), the photothreshold, and further the activation energy (ΔE) analyzed from the Arrhenius plot of NT values obtained in the temperature increase and subsequent temperature decrease processes. In this study, we re-examined the dependence of the TPPE data from two types of Cu metal surfaces: sample A, which was mechanically abraded in alcohols, water, and air, and sample C, which was only ultrasonically cleaned in these liquids. The NT for both samples slowly increased with increasing temperature, reached a maximum (NTmax) at 250 °C (maximum temperature, Tmax), and after that, decreased. For sample A, the NTmax value decreased in the order H2O > CH3OH > C2H5OH > (CH3)2CHOH > C3H7OH, although the last alcohol gave Tmax = 100 °C, while with sample C, the NTmax value decreased in the order C3H7OH > (CH3)2CHOH > C2H5OH > CH3OH > H2O. Interestingly, both orders of the liquids were completely opposite; this means that a Cu surface can possess a two-way character. The NT intensity was found to be strongly associated with the change from the hydroxyl group (–Cu–OH) to the oxide oxygen (O2−) in the O1s spectra in the XPS measurement. The difference between the above orders was explained by the acid–base interaction mode of the –Cu–OH group with the adsorbed molecule on the surfaces. The H2O adsorbed on sample A produces the electric dipole –CuOδ−Hδ+ ⋅⋅⋅ :OH2 (⋅⋅⋅ hydrogen bond), while the C3H7OH and (CH3)2CHOH adsorbed on sample C produce RO−δHδ+ ⋅⋅⋅ :O(H)–Cu− (R = alkyl groups). Gutmann's acceptor number (AN) representing the basicity of the liquid molecules was found to be related to the TPPE characteristics: (CH3)2CHOH (33.5), C2H5OH (37.1), CH3OH (41.3), and H2O (54.8) (the AN of C3H7OH could not be confirmed). With sample A, the values of NTmaxa and ΔEaUp1 both increased with increasing AN (Up1 means the first temperature increase process). On the other hand, with sample C, the values of NTmaxc and ΔEcUp1 both decreased with increasing AN. These findings suggest that sample A acts as an acid, while sample C functions as a base. However, in the case of both types of samples, A and C, the NTmax values were found to increase with increasing ΔEUp1. It was explained that the ΔEUp1 values, depending on the liquids, originate from the difference in the energy level of the hydroxyl group radical at the surface denoted. This is able to attract electrons in the neighborhood of the Fermi level of the base metal through tunnelling. After that, Auger emission electrons are released, contributing to the ET in the overlayer. These electrons are considered to have a strong ability of reducibility. [ABSTRACT FROM AUTHOR]

Using the Fenton reaction, a system has been modeled in which particles similar to those formed during the radiolysis of water were generated. The suppression of reactions caused by hydroxyl radicals formed in the system under the action of chlorophyllin is evaluated by the chemiluminescence method. It has been shown that sodium-copper chlorophyllin dose-dependently inhibits the chemiluminescence accompanying the phosphatidic acid peroxidation induced by the Fenton reaction. Based on this, it is concluded that copper chlorophyllin can inhibit the metabolism of lipid radiotoxins, lipid peroxidation (LP), caused by the attack of water radiolysis products on lipid molecules. [ABSTRACT FROM AUTHOR]

The review considers the problem of hydrogen peroxide decomposition and hydroxyl radical formation in the presence of iron in vivo and in vitro. Analysis of the literature data allows us to conclude that, under physiological conditions, transport of iron, carried out with the help of carrier proteins, minimizes the possibility of appearance of free iron ions in cytoplasm of the cell. Under pathological conditions, when the process of transferring an iron ion from a donor protein to an acceptor protein can be disrupted due to modifications of the carrier proteins, iron ions can enter cytosol. However, at pH values close to neutral, which is typical for cytosol, iron ions are converted into water-insoluble hydroxides. This makes it impossible to decompose hydrogen peroxide according to the mechanism of the classical Fenton reaction. A similar situation is observed in vitro, since buffers with pH close to neutral are used to simulate free radical oxidation. At the same time, iron hydroxides are able to catalyze decomposition of hydrogen peroxide with formation of a hydroxyl radical. Decomposition of hydrogen peroxide with iron hydroxides is called Fenton-like reaction. Studying the features of Fenton-like reaction in biological systems is the subject of future research. [ABSTRACT FROM AUTHOR]

• Surface Fe (oxyhydr)oxides mediated electron transfer to promote HO• production. • Corrosion of surface oxides and quenching of HO• by Cl− inhibited HO• production. • Formation of surface Fe(II)-CO 2 complexes increased average rate of HO• production. • Photoelectrons generated by UV irradiation promoted extensive production of HO•. Pyrite is widely distributed in estuarine sediments as an inexpensive natural Fenton-like reagent, however, the mechanism on the hydroxyl radical (HO·) production by pyrite under estuarine environmental conditions is still poorly understood. The batch experiments were performed to investigate the effects of estuarine conditions including aging (in air, in water), seawater anions (Cl−, Br− and HCO 3 −) and light on the HO· production by pyrite oxidation. The one-electron transfer dominated the process from O 2 to HO· induced by oxidation of pyrite. The Fe (oxyhydr)oxide coatings on the surface of pyrite aged in air and water consumed hydrogen peroxide while mediating the electron transfer, and the combined effect of the two resulted in a suppression of HO· production in the early stage of aging and a promotion of HO· production in the later stage of aging. Corrosion of the surface oxide layers by aggressive anions was the main reason for the inhibition of HO· production by Cl− and Br−, and the generation of Cl· and Br· may also play a role in the scavenging of HO·. HCO 3 − increased the average rate of HO· production through surface-CO 2 complexes formed by adsorption on the surface of pyrite. The significant enhancement of HO· production under light was attributed to the formation of photoelectrons induced by photochemical reactions on pyrite and its surface oxide layers. These findings provide new insights into the environmental chemical behavior of pyrite in the estuary and enrich the understanding of natural remediation of estuarine environments. [Display omitted] [ABSTRACT FROM AUTHOR]

· The fragmentation of cationic resin was studied using the statistical fragmentation model. · The degradation of cationic resin by ·OH was calculated by DFT. · Active sites of cationic resin monomer were predicted. · Dihydroxy addition and elimination reactions played a major role. · The decomposition mechanisms were proposed by combing physical models and chemical calculations. The treatment and disposal of radioactive waste are presently facing great challenges. Spent ion exchange resins have become a focus of attention due to their high production and serious environmental risks. In this paper, a simplified model of cationic exchange resin is proposed, and the degradation processes of cationic resin monomer initiated by hydroxyl radicals (·OH) are clarified by combining statistical molecular fragmentation (SMF) model and density functional theory (DFT) calculations. The prediction of active sites indicates that the S-O bonds and the C-S bond of the sulfonic group are more likely to react during the degradation. The meta -position of the sulfonic group on the benzene ring is the most active site, and the benzene ring without the sulfonic group has a certain reactivity. The C11-C14 and C17-C20 bonds, on the carbon skeleton, are the most easily broken. It is also found that dihydroxy addition and elimination reactions play a major role in the process of desulfonation, carbon skeleton cleavage and benzene ring separation. The decomposition mechanisms found through the combination of physical models and chemical calculations, provide theoretical guidance for the treatment of complex polycyclic aromatic hydrocarbons. [Display omitted] [ABSTRACT FROM AUTHOR]

Recently, granular activated carbon (GAC) has shown its effectiveness as a cathode material for in situ ROS generation. Here, we present an electrochemically modified GAC cathode using electrode polarity reversal (PR) approach for enhanced H2O2 decomposition via 2-electron oxygen reduction reaction (2e-ORR). The successful GAC modification using PR necessitates tuning of the operational parameters such as frequency, current, and time intervals between the PR cycles. This modification enhances the GAC hydrophilicity by increasing the density of surface oxygen functionalities. After optimization of the electrode polarity, using the 20 (No PR)-2 (PR) interval and 140 mA current intensity, the •OH concentration reaches 38.9 μ M compared to the control (No PR) (28.14 μ M ). Subsequently, we evaluated the enhanced •OH generation for the removal of glyphosate, a persistent pesticide used as a model contaminant. The modified GAC using PR removed 67.6% of glyphosate compared to 40.6% by the unmodified GAC without PR, respectively. The findings from this study will advance the utilization of GAC for in situ ROS synthesis, which will have direct implications on increasing the effectiveness of electrochemical water treatment systems. [ABSTRACT FROM AUTHOR]

The presence of residual organic pollutants in aquaculture water contributes to water quality degradation, impacts the quality of aquatic products, and hinders the sustainable development of the aquaculture industry. The photo-Fenton oxidation technology, which integrates sunlight into the traditional Fenton reaction, has become one of the research hotspots in the field of water treatment due to its broad pH response range, high yield of reactive radicals, and efficient mineralization of organic pollutants. This paper systematically summarizes the fundamental principles underlying photo-Fenton oxidation technology, analyzes the prevalent catalysts employed in photo-Fenton oxidation system, and discusses the factors influencing the efficiency of photo-Fenton oxidation system, as well as its application in the treatment of representative emerging contaminants in water. It is pointed out that the development of novel catalysts capable of achieving on-site photochemical generation of H2O2 and enhancing the stability and recyclability of the catalyst is the key to realizing the engineering application of the photo-Fenton oxidation system, thereby offering theoretical support for the application of this technology in aquaculture water treatment. [ABSTRACT FROM AUTHOR]

In this study, the influence of HCO3− on NO3−-induced photosensitive degradation of sulfamethoxazole (SMX) under UV irradiation was investigated. It was found that the removal of SMX by UV in the presence of NO3− improved significantly compared to its photolysis, which was confirmed to be due to the role of hydroxyl radical (HO•) formed through UV-activated NO3−. However, the addition of HCO3− in UV/NO3− system could further enhance SMX degradation, which was verified to be ascribed to the formed carbonate radical (CO3•−) through the reaction of HCO3− with HO•. The second-order rate constant of CO3•− with SMX was determined to be 2.58 × 108 M−1 s−1. In UV/NO3−/HCO3− system, the reactive species for SMX removal were HO• and CO3•−, and the contribution of CO3•− to SMX degradation might be much higher than that of HO•. The concentration of NO3− was almost unchanged after reaction in UV/NO3− and UV/NO3−/HCO3− systems because of its regeneration. Based on the detected four transformation products, the possible degradation pathways of SMX in UV/NO3−/HCO3− system were proposed including hydroxylation, amino-oxidation and bond cleavage. [ABSTRACT FROM AUTHOR]

Daidzein (DAID), as a common phytoestrogen, is often detected in the environment. In this paper, the photodegradation mechanism and UV absorption spectra of three different dissociation forms of DAID in water were studied by density functional theory (DFT) and time-dependent density functional theory (TDDFT). The photodegradation mechanism includes direct photolysis and indirect photolysis by reacting with ·OH in water. The reaction types of indirect photolysis of DAID0 with ·OH are OH-addition and H-abstraction, and H-abstraction is more favorable than OH-addition. The indirect photolysis reaction type of DAID− and DAID2− with ·OH is OH-addition. The degree of difficulty in the reaction of the three dissociation forms of DAID in water with ·OH is: DAID0 < DAID− < DAID2−. Results have shown that DAID can undergo degradation and can be transformed by reacting with ·OH in water. In addition, the direct photolysis reaction is also considered in the excited state to reveal the mechanism of the photochemical reaction. The direct photolysis pathway of DAID in water is the cleavage of C–C bond and C–O bond, but the Ea values required for these reactions are higher than the Ea values for the indirect photolysis reactions, indicating that direct photolysis is not the main pathway of photodegradation. The method of quantum chemical calculation in this study is helpful to understand the photochemical transformation of DAID in water. [ABSTRACT FROM AUTHOR]

Fine particulate matter (PM2.5) is a major air pollutant in most cities of China, and poses great health risks to local residents. In this study, the health effects of PM2.5 in Nanjing and Yangzhou were compared using computational and experimental methods. The global exposure mortality model (GEMM), including the results of a cohort study in China, was used to estimate the disease-related risks. Premature mortality attributable to PM2.5 exposure were markedly higher in Nanjing than that in Yangzhou at comparable levels of PM2.5 (8191 95% CI, 6975–9994 vs. 6548 95% CI, 5599–8049 in 2015). However, the baseline mortality rate was on a country-level and the age distribution was on a province-level, traditional estimation method could not accurately represent the health burdens of PM2.5 on a city-level. We proposed a refined calculation method which based on the actual deaths of each city and the disease death rates. Conversely, similar concentrations of PM2.5 exposure resulted in higher actual deaths per million population in Yangzhou (1466 95% CI, 1266–1746) than that in Nanjing (1271 95% CI, 1098–1514). Health risks of PM2.5 are associated with the generation of reactive oxygen species, among which hydroxyl radial (·OH) is the most reactive one. We then collected these PM2.5 samples and quantified the induced ·OH. Consistently, average ·OH concentration in 2015 was higher in Yangzhou than that in Nanjing, again indicating that PM2.5 in Yangzhou was more toxic. The combination of computational and experimental methods demonstrated the complex relationship between health risks and PM2.5 concentrations. The refined estimation method could help us better estimate and interpret the risks caused by PM2.5 exposure on a city-level. [ABSTRACT FROM AUTHOR]

A comparative study on the mineralization of antibiotic trimethoprim (TMP) in neutral medium was investigated by applying irradiation with five types of ultraviolet lamps. Among these lamps, the whole envelope of one lamp contained ordinary quartz, which could only transmit ultraviolet-C (UVC) light. For the other four lamps, approximately one tenth, a quarter, a half, and full of envelopes were comprised of high-purity synthetic quartz, which can transmit both vacuum ultraviolet (VUV) and UVC light. TMP decay was well fitted to pseudo-first-order reaction kinetics and occurred more quickly as the VUV intensity increased. Poor mineralization was achieved in the absence of VUV light, whereas the mineralization efficiency was also enhanced with increasing VUV intensity. The presence of hydroxyl radicals (•OH), superoxide radicals (O2•−) and singlet oxygen (1O2) during VUV photolysis of water was confirmed by electron paramagnetic resonance (EPR) analysis. Appropriate radical quenching experiments and fluorescent molecular probe detection provided the evidence that •OH played a significant role in TMP mineralization. Higher VUV intensity favored the generation of H2O2 and •OH. The evolution of NH4+ and NO3− as well as carboxylic acids (formic, acetic, oxalic, and oxamic acids) released in the treated solution were quantified. Ten aromatic intermediates were also identified by UPLC-QTOF-MS. Thereby, a plausible reaction sequence for TMP mineralization in VUV/UVC photolysis was finally proposed. [ABSTRACT FROM AUTHOR]

DFB diode laser at 1434 nm was used to detect the hydroxyl radical OH in the first overtone region. Experiments were made at the most intense line Q(3/2) of 2Π3/2 electronic term. Collisional broadening for He buffer gas was measured. Using reliably defined integrated intensity of this line and calculated line contour, the absorption cross section could be obtained for different pressures. This enables measurement of the absolute concentration of OH in time-resolved experiments without calibration. The minimum concentration of radicals detected by absorption is 2 × 1012 cm–3 with the resolving time approximately 10–6 s. [ABSTRACT FROM AUTHOR]

Water contamination engendered by pharmaceutical effluents and organic dyes is emerged as a serious environmental catastrophe, causing massive ecological repercussions as well as enduring risks to aquatic life and human health. Hence designing of highly efficient and robust photocatalyst with excellent intrinsic properties for the degradation of pollutants is desirable. In this research, a visible-light-responsive cerium manganese oxide (CeMnO3) perovskite nanomaterial was synthesized via facile citrate sol–gel approach to address the deterioration of tetracycline hydrochloride (TcH) antibiotic and methylene blue (MB) dye residues for the first time in aqueous media. The CeMnO3 nanostructure was characterized through XRD, XPS, FTIR, FESEM, EDS, PL, and UV–Vis spectrophotometer to disclose the catalytic functionalities, crystallographic structures, elemental interaction, structural configuration, surface morphology, and other intrinsic optical features of the material. The CeMnO3 catalyst exhibits eminent photocatalytic activity for the degradation of TcH and MB residues under visible light sources attributed to the narrow bandgap energy (2.50 eV) achieved in CeMnO3 perovskite nanomaterial. As-prepared catalysts achieved an optimum efficiency of about 89% and 95% for the photocatalytic degradation of TcH (10 mg/L) and MB (10 mg/L) for 30 mg and 25 mg catalyst dosage in 90 min, respectively. The radical scavenger test revealed that the hydroxyl radical · OH and superoxide radicals · O 2 - are the chief reactive oxidizing agents in the photocatalytic degradation process. Furthermore, even after three subsequent cycles, the catalyst stays stable and demonstrates an excellent degradation efficiency, validating its potential cyclic capability and chemical stability. The current work proposes an intriguing strategy to fabricate a CeMnO3 catalyst with high-performance detoxification of TcH and MB residual compounds which are widely used and frequently reported for their contaminations in the ambient environment. [ABSTRACT FROM AUTHOR]

We obviously agree with Wu et al. that H2O2 might accumulate in the Archean land waters devoid of Fe2+. We do disagree on the topic of the half-life of H2O2, as the work cited in support for a longer half-live is not relevant to the conditions in the Archean ocean. While the existence of radicals in quartz is not in doubt, we do question the hypothesis that these radicals oxidize water to HO• and H2O2.

The hydroxyl radical (OH) is the most important oxidant on global and local scales in the troposphere. Urban OH controls the removal rate of primary pollutants and triggers the production of ozone. Interannual trends of OH in urban areas are not well documented or understood due to the short lifetime and high spatial heterogeneity of OH. We utilize machine learning with observational inputs emphasizing satellite remote sensing observations to predict surface OH in 49 North American cities from 2005 to 2014. We observe changes in the summertime OH over one decade, with wide variation among different cities. In 2014, compared to the summertime OH in 2005, 3 cities show a significant increase of OH, whereas, in 27 cities, OH decreases in 2014. The year-to-year variation of OH is mapped to the decline of the NO2 column. We conclude that these cities in this analysis are either in the NOx-limited regime or at the transition from a NOx suppressed regime to a NOx-limited regime. The result emphasizes that, in the future, controlling NOx emissions will be most effective in regulating the ozone pollution in these cities.

The degradation of a mixture of ibuprofen, naproxen, and diclofenac in various effluents by UVC/H2O2 or UVC/S2O82− was studied to assess the impact of the matrix composition and of the oxidant precursor on process efficiency. Experiments were carried out in a 20-L laboratory pilot (a scaled-down version of a full-scale pilot). In effluents collected during dry weather, the rural constructed wetland effluent allowed faster degradation than the urban conventional WWTP effluent, regardless of the nature of the targets or of the oxidant precursor. This was mainly attributed to a three-times higher chemical oxygen demand in the urban effluent, likely to quench the oxidative species. UV fluences to reach 90% degradation of the three compounds were 3,800 and 5,500 mJ cm−2 in the rural effluent, whereas they were 6,600 and 6,100 mJ cm−2 in the urban effluent with H2O2 and S2O82−, respectively. After a rainfall event, the rural effluent composition was not significantly affected compared to that of the urban effluent that underwent the dilution effect. Therefore, the stability of the rural effluent composition allowed comparable degradation efficiency, whereas the dilution effect led to a significant increase in the degradation rate constants in the urban effluent (up to four times higher). HIGHLIGHTS UVC-based process efficiency varies with weather and effluent composition.; Downstream effluent composition seems more consistent in a rural constructed wetland than in an urban WWTP.; UVC-based AOPs are more appropriate to treat effluents with low and consistent organic matter concentration.; allows for faster degradation of NAP and H2O2 for faster degradation of IBU.;

Herein, we systematically investigated the mechanisms of OH production and arsenic (As(III)) oxidation induced by sulfur vacancy greigite (Fe3S4) under anoxic and oxic conditions. Reactive oxygen species analyses revealed that sulfur vacancy-rich Fe3S4 (SV-rich Fe3S4) activated molecular oxygen to produce hydrogen peroxide (H2O2) via a two-electron reduction pathway under oxic conditions. Subsequently, H2O2 was decomposed to OH via the Fenton reaction. Additionally, H2O was directly oxidized to OH by surface high-valent iron (Fe(IV)) resulting from the abundance of sulfur vacancies in Fe3S4 under anoxic/oxic conditions. These differential OH-generating mechanisms of Fe3S4 resulted in higher OH production of SV-rich Fe3S4 compared to sulfur vacancy-poor Fe3S4 (SV-poor Fe3S4). Moreover, the OH production rate of SV-rich Fe3S4 under oxic conditions (19.3 ± 1.0 μM•h-1) was 1.6 times greater than under anoxic conditions (11.8 ± 0.4 μM•h-1). As(III) removal experiments and X-ray photoelectron spectra (XPS) showed that both OH production pathways were favorable for As(III) oxidation, and a higher concentration of As(V) was immobilized on the surface of SV-rich Fe3S4 under oxic conditions. This study provides new insights concerning OH production and environmental pollutants removal mechanisms on surface defects of Fe3S4 under anoxic and oxic conditions.

X-ray radiolytic labeling uses broadband X-rays for in situ hydroxyl radical labeling to map protein interactions and conformation. High flux density beams are essential to overcome radical scavengers. However, conventional sample delivery environments, such as capillary flow, limit the use of a fully unattenuated focused broadband beam. An alternative is to use a liquid jet, and we have previously demonstrated that use of this form of sample delivery can increase labeling by tenfold at an unfocused X-ray source. Here we report the first use of a liquid jet for automated inline quantitative fluorescence dosage characterization and sample exposure at a high flux density microfocused synchrotron beamline. Our approach enables exposure times in single-digit microseconds while retaining a high level of side-chain labeling. This development significantly boosts the method's overall effectiveness and efficiency, generates high-quality data, and opens up the arena for high throughput and ultrafast time-resolved in situ hydroxyl radical labeling.

The widespread presence and use of Bisphenol A (BPA) in aquatic environments has caused significant ecological damage. Coal gangue (CG), a byproduct of coal mining, poses a major environmental concern due to its vast land occupation and potential for pollution. A magnetic recyclable geopolymer (MnFe2O4-CGP) using coal gangue geopolymer (CGP) as the carrier was successfully synthesized and was evaluated for its ability to Fenton-like degrade BPA. The characterization techniques revealed the successful incorporation of spherical MnFe2O4 onto the CGP surface and that CGP serves as an excellent platform for the immobilization and dispersion of MnFe2O4. The degradation rate reached 100% within 60 min at pH = 5, 15 mmol/L H2O2, 0.6 g/L catalyst, and 50 mg/L BPA, significantly higher than MnFe2O4 and CGP alone. It was indicated that the degradation rate of BPA in MnFe2O4-CGP composites was 0.1121 min−1, which was consistent with the first-order kinetic model. The saturation magnetization of MnFe2O4-CGP was measured to be 10.96 emu/g, enabling convenient recovery. MnFe2O4-CGP exhibited excellent stability, as the degradation rate of BPA remained above 95% even after five reaction cycles. This efficiency may be due to the MnFe2O4-CGP induced generation of reactive radicals. Quenching and EPR radical trapping experiments unequivocally confirmed that the reactive radical was hydroxyl radical (•OH). These results indicate that MnFe2O4-CGP has potential application prospects as a magnetic recyclable geopolymer composite in Fenton-like catalysis.

The hydroxyl radical (OH) oxidation of the most abundant nonmethane volatile organic compound emitted to the atmosphere, isoprene (C5H8), produces a number of chemical species that partition to the condensed phase via gas-particle partitioning or form condensed-phase compounds via multiphase/heterogeneous chemistry to generate secondary organic aerosols (SOA). The SOA species in aerosol water or cloud/fog droplets may oxidize further via aqueous reaction with OH radicals, among other fates. Rate coefficients for compounds in isoprene's photochemical cascade are well constrained in the gas phase; however, a gap of information exists for the aqueous OH rate coefficients of the condensed-phased products, precluding the atmospheric modeling of the oxidative fate of isoprene-derived SOA. This work investigated the OH-initiated oxidation kinetic rate coefficients (kOH) for six major SOA compounds formed from the high-NO and low-NO channels of isoprene's atmospheric oxidation and one analog, most of which were synthesized and purified for study: (k1) 2-methyltetrol [MT: 1.14 (±0.17) × 109 M-1 s-1], (k2) 2-methyl-1,2,3-trihydroxy-4-sulfate [MT-4-S: 1.52 (±0.25) × 109 M-1 s-1], (k3) 2-methyl-1,2-dihydroxy-3-sulfate [MD-3-S: 0.56 (±0.15) × 109 M-1 s-1], (k4) 2-methyl-1,2-dihydroxy-but-3-ene [MDE: 4.35 (±1.16) × 109 M-1 s-1], (k5) 2-methyl-2,3-dihydroxy-1,4-dinitrate [MD-1,4-DN: 0.24 (±0.04) × 109 M-1 s-1], (k6) 2-methyl-1,2,4-trihydroxy-3-nitrate [MT-3-N: 1.12 (±0.15) × 109 M-1 s-1], and (k7) 2-methylglyceric acid [MGA: pH 2:1.41 (±0.49) × 109 M-1 s-1; pH 5:0.97 (±0.42) × 109 M-1 s-1]. The second-order rate coefficients are determined against the known kOH of erythritol in pure water. The decays of each reagent were measured with nuclear magnetic resonance (NMR) and high-performance liquid chromatography-high resolution mass spectrometry (HPLC-HRMS). The aqueous photooxidation fates of isoprene-derived SOA compounds are substantial and may impact the SOA budget when implemented into global models.

Air pollution is a major risk factor for human health. Chemical reactions in the epithelial lining fluid (ELF) of the human respiratory tract result in the formation of reactive oxygen species (ROS), which can lead to oxidative stress and adverse health effects. We use kinetic modeling to quantify the effects of fine particulate matter (PM2.5), ozone (O3), and nitrogen dioxide (NO2) on ROS formation, interconversion, and reactivity, and discuss different chemical metrics for oxidative stress, such as cumulative production of ROS and hydrogen peroxide (H2O2) to hydroxyl radical (OH) conversion. All three air pollutants produce ROS that accumulate in the ELF as H2O2, which serves as reservoir for radical species. At low PM2.5 concentrations (10 μg m-3), however, Fenton chemistry overwhelms the ROS buffering effect and leads to a tipping point in H2O2 fate, causing a strong nonlinear increase in OH production. This shift in ROS chemistry and the enhanced OH production provide a tentative mechanistic explanation for how the inhalation of PM2.5 induces oxidative stress and adverse health effects.

In the method of X-ray footprinting mass spectrometry (XFMS), proteins at micromolar concentration in solution are irradiated with a broadband X-ray source, and the resulting hydroxyl radical modifications are characterized using liquid chromatography mass spectrometry to determine sites of solvent accessibility. These data are used to infer structural changes in proteins upon interaction with other proteins, folding, or ligand binding. XFMS is typically performed under aerobic conditions; dissolved molecular oxygen in solution is necessary in many, if not all, the hydroxyl radical modifications that are generally reported. In this study we investigated the result of X-ray induced modifications to three different proteins under aerobic versus low oxygen conditions, and correlated the extent of damage with dose calculations. We observed a concentration-dependent protecting effect at higher protein concentration for a given X-ray dose. For the typical doses used in XFMS experiments there was minimal X-ray induced aggregation and fragmentation, but for higher doses we observed formation of covalent higher molecular weight oligomers, as well as fragmentation, which was affected by the amount of dissolved oxygen in solution. The higher molecular weight products in the form of dimers, trimers, and tetramers were present in all sample preparations, and, upon X-ray irradiation, these oligomers became non-reducible as seen in SDS-PAGE. The results provide an important contribution to the large body of X-ray radiation damage literature in structural biology research, and will specifically help inform the future planning of XFMS, and well as X-ray crystallography and small-angle X-ray scattering experiments.

The heterogeneous Fenton process is a strategy for overcoming the greatest shortcomings of traditional homogeneous Fenton, i.e. the high generation of ferric hydroxide sludge and effectivity in a limited pH range. In this study, we constructed a heterogeneous Fenton system with natural iron-bearing clay mineral (nontronite) and dimethoxyhydroquinone (DMHQ) to degrade lincomycin (LCM) without the addition of H2O2. The degradation mechanism was derived from the hydroxyl radicals (•OH) produced from the oxygenation of Fe(II) in nontronites, which was reduced by DMHQ. Acidic conditions and low concentrations of LCM were favourable for LCM degradation. When the solution pH increased from 3 to 7, the final LCM removal ratio decreased from 95 to 46%. However, LCM can still be degraded by 46% under neutral conditions and 20% at the LCM concentration of 500 μmol/L. The nontronite has good reusability, and the LCM degradation efficiency in the fourth cycle still exceeded 90% of the original efficiency. The degradation sites of LCM mainly occurred in the methyl thioether moiety and the aliphatic amine group on the pyrrolidine ring, with the final product of CO2. This research presents a new eco-friendly and cost-effective method for the heterogenous Fenton process without external H2O2. HIGHLIGHTS 2,6-DMHQ could reduce structural Fe(III) to form Fe(II) to react with O2 and yield •OH.; LCM could be effectively degraded in the nontronite/2,6-DMHQ reaction system.; The nontronite was efficient with good reusability material.; The clay mineral not only provides iron but also a constrained reaction environment.; The reaction system is efficient, simple, and does not need H2O2 addition.;

Abstract Carbon materials (e.g., pyrogenic carbon (PyC)) are widely used in agricultural soils and can participate in various biogeochemical processes, including iron (Fe) cycling. In soils, Fe(II) species have been proposed as the main active contributor to produce reactive oxygen species (ROS), which are involved in various biogeochemical processes. However, the effects of PyC on the transformation of different Fe species in soils and the associated production of ROS are rarely investigated. This study examined the influence of PyC (pyrolyzed at 300–700 °C) on Fe(II)/Fe(III) cycling and hydroxyl radical (·OH) production during redox fluctuations of paddy soils. Results showed that the reduction of Fe(III) in soils was facilitated by PyC during anoxic incubation, which was ascribed to the increased abundance of dissimilatory Fe(III)-reducing microorganisms (biotic reduction) and the electron exchange capacity of PyC (abiotic reduction). During oxygenation, PyC and higher soil pH promoted the oxidation of active Fe(II) species (e.g., exchangeable and low-crystalline Fe(II)), which consequently induced higher yield of ·OH and further led to degradation of imidacloprid and inactivation of soil microorganisms. Our results demonstrated that PyC accelerated Fe(II)/Fe(III) cycling and ·OH production during redox fluctuations of paddy soils (especially those with low content of soil organic carbon), providing a new insight for remediation strategies in agricultural fields contaminated with organic pollutants. Graphical Abstract

Background and Objective: Vacuum Ultraviolet (VUV)-based advanced oxidation is a new category of advanced purification processes, so this study aimed to compare the efficiency of VUV and Ultraviolet-C (UVC) processes in combination with H2O2 and PMS in degrading Remdesivir. Materials and Methods: The photoreactor was investigated with VUV and UVC lamps in combination with H2O2 and PMS for Remdesivir degradation. Also, the effect of variables such as solution pH, H2O2 dose, Remdesivir concentration, the presence of radical scavengers and anions, as well as hydraulic retention time was considered in the continuous process of Remdesivir removal. Results: The findings showed that the optimal pH in the processes of VUV, UVC, and their derivatives was equal to 7. By adding 1 mM of PMS and H2O2 to the VUV process, the degradation efficiency of Remdesivir was increased from 92.2 ± 0.4% to 98.3 ±2.1% and 100 ± 0.3%, respectively, after 30 min. Also, in the UVC process combined with H2O2 and PMS, the degradation efficiency reached 77.8 ± 1.5 and 85.2 ± 1.3% after 40 min, respectively. The degradation kinetics in the examined processes were as follows: VUV/H2O2 > VUV/PMS > VUV > UVC/H2O2 > UVC/PMS > UVC. The hydroxyl radical was the main reactive oxygen species that led to the decomposition of Remdesivir. The continuous operation of VUV/H2O2 showed that the removal efficiency of Remdesivir reached 94.7 ±0.8% after 40 min. Conclusion: Considering the high rate of Remdesivir degradation by adding H2O2, the VUV/H2O2 process can be introduced as an efficient technology for the removal of antiviral drugs.

Developing a photocatalyst for environmental remediation with extortionate visible light absorption capability and low reunion of photogenerated charge carriers is of tremendous interest. Considering this, the present work reports the fabrication of a low-cost and eco-friendly Fe-doped WO3/BiVO4 photocatalyst prepared by the facile one-step hydrothermal technique. The photocatalyst outperformed in the removal of rhodamine B dye than the pristine samples. The XRD and Raman spectroscopy analysis affirms the successful doping of the Fe cations within the WO3 crystal structure. The absorption studies reveal the redshift to higher wavelengths which elucidates the enhancement of oxygen vacancy, and the band gap value changes are also apparent due to the heterojunction scheme of the photocatalyst. The time-resolved photoluminescence studies substantiate the effective reduction in the recombination rate with an average lifetime of 364 ns proving it to be an effective photocatalyst for the removal of rhodamine B dye. The catalyst revealed outstanding performance with 94.3 % removal of rhodamine B dye within 6 h. However, the removal efficiency was higher at pH 14 with a degradation of 92.6 % (100 min) corroborating that the influence of hydroxyl radical greatly facilitates a Fenton-like reaction that provokes the degradation process faster. It was further confirmed from the scavenging analysis that, with the addition of an H2O2 scavenger the degradation rate is fast due to the formation of hydroxyl radicals that emerged from the fusion of H2O2 with superoxide radicals. This outperformance validates the competency of the photocatalyst in the removal of organic pollutants.

Vacuum ultraviolet (VUV, 185 + 254 nm) irradiation performs well for oxidation of model pollutants. However, oxidation of pollutants does not necessarily lead to a reduction in toxicity. Currently, a comprehensive understanding of the effect of VUV irradiation on the toxicity of real wastewater is still lacking. In this study, the influence of VUV irradiation on the toxicity of secondary effluents to Chinese hamster ovary (CHO) cells was investigated. The induction units of endogenous reactive oxygen species (ROS) and 8-hydroxyguanosine (8-OHdG) in cells continuously decreased with prolonged irradiation time. After 36 min of irradiation, the cytotoxicity and the genotoxicity of the secondary effluents were reduced by 57%–63% and 56%–61%, respectively. The UV (254 nm), •OH, and other substances generated during the VUV irradiation directly drive toxicity changes of wastewater. The contribution of •OH generated during VUV irradiation to the reductions in cytotoxicity and genotoxicity of the secondary effluents reached 72%–78% and 77%–84%, respectively. Hydroxyl radicals generated during VUV irradiation played an important role in the detoxification. The relative signal intensity of dissolved organic carbon (DOC) > 500 Da was partially removed, whereas that of DOC 500 Da in the samples was much lower than that of DOC

Diclofenac (DCF) is a synthetic, non-steroidal anti-inflammatory drug. It is a persistent chemical that resists biological degradation and is difficult to completely remove by conventional wastewater treatment plants (WWTP). In recent years, various advantage oxidation processes (AOPs), including photocatalytic processes such as the TiO2/UV process, have been applied for DCF treatment in wastewater. In this study, a heterogeneous photocatalysis process combined with H2O2 was applied for DCF removal in synthesized wastewater. The results show that the optimum conditions for DCF removal by the photocatalysis process were a pH of 6.5 and an initial TiO2 concentration of 1 g/L. The removal efficiency of DCF at a concentration of 50 mg/L by the photocatalysis process was 65.25 % after a 150-min reaction time. A combination photocatalysis process with H2O2 can enhance DCF removal efficiency. The DCF concentration in solution was completely reduced after 150 minutes of reaction time by the UV/TiO2/H2O2 process. The optimum initial H2O2 concentration for this study was 10 ml/L.

The hydroxyl radical (•OH) is shown to play a crucial role in the occurrence and progression of acute kidney injury (AKI). Therefore, the development of a robust •OH probe holds great promise for the early diagnosis of AKI, high‐throughput screening (HTS) of natural protectants, and elucidating the molecular mechanism of intervention in AKI. Herein, the design and synthesis of an activatable fluorescent/photoacoustic (PA) probe (CDIA) for sensitive and selective imaging of •OH in AKI is reported. CDIA has near‐infrared fluorescence/PA channels and fast activation kinetics, enabling the detection of the onset of •OH in an AKI model. The positive detection time of 12 h using this probe is superior to the 48‐hour detection time for typical clinical assays, such as blood urea nitrogen and serum creatinine detection. Furthermore, a method is established using CDIA for HTS of natural •OH inhibitors from herbal medicines. Puerarin is screened out by activating the Sirt1/Nrf2/Keap1 signaling pathway to protect renal cells in AKI. Overall, this work provides a versatile and dual‐mode tool for illuminating the •OH‐related pathological process in AKI and screening additional compounds to prevent and treat AKI. [ABSTRACT FROM AUTHOR]

Iron(II) species can participate in the Fenton and Fenton‐like reactions to generate the hydroxyl radical that can oxidatively damage biomolecules and induce oxidative stress in biological systems. Many diseases, including neurodegeneration, cardiovascular disease and cancer, are associated with oxidative stress. However, it is proposed recently that hydroxyl radical would not be generated from the Fenton reaction under physiological conditions and thus would not cause oxidative stress in biological systems. This proposal may cause confusion for understanding oxidative stress and can also have impact on therapeutic strategies for the diseases associated with oxidative stress. In this Mini-review, the up-to-date convincing evidences of hydroxyl radical generation from the physiologically relevant Fenton‐like reactions of the iron(II) complexes with physiological ligands in human blood plasma, including histidine, citrate and phosphate, are succinctly reviewed. The oxidative damages caused by hydroxyl radical to biomolecules and cells are briefly summarized. These findings strongly challenge the above proposal. [Display omitted] • Fenton/Fenton‐like reactions of Fe(II) species can generate hydroxyl radical (●OH) • But a proposal doubts ●OH generation in physiology and its role in oxidative stress • Herein findings of ●OH generation in physiologically relevant Fenton‐like reactions • Evidences of ●OH caused oxidative damages to biomolecules and cells are addressed • These findings strongly challenge the above proposal [ABSTRACT FROM AUTHOR]

Oxidation by metal activated persulfate and peroxide produces sulfate radicals ( SO 4 • − ) and hydroxyl radicals ( ∙ O H), powerful oxidants that can be used for the destruction of a wide range of pollutants in water and wastewater. In this study, methylene blue dye was used as an indicator to determine the reaction kinetics and identify the radicals produced during oxidation by persulfate, which was added in the form of monopersulfate, and peroxide in the presence of ferrous ions. There was a positive correlation between the monopersulfate concentration and the degradation of methylene blue in the absence of ferrous ions at pH 3, 5, and 7. In the absence of ferrous ions, peroxide had little to no effect on the degradation of methylene blue. Fe2+/monopersulfate and Fe2+/peroxide systems at a ratio of 0.5:1 resulted in the rapid degradation (<20 min) of methylene blue. Humic acid, at a concentration as high as 20 mg/L, did not affect the degradation kinetics in both systems. Bicarbonate inhibited the Fe2+/peroxide reaction; however, in the Fe2+/monopersulfate system, the scavenging effect of bicarbonate was inhibited at higher concentrations, that is, <100mM. The dominant radical species in Fe2+/monopersulfate system was identified as the SO 4 • − using ethanol and tert-butyl alcohol as probes. This screening method was validated by using the same oxidation conditions for the degradation of microcystin-LR (MC-LR). Similar reaction kinetics were observed between MC-LR and monopersulfate. Fe2+/monopersulfate and Fe2+/peroxide reactions resulted in the rapid degradation of MC-LR. Humic acid and bicarbonate had a similar effect on the MC-LR degradation. SO 4 • − was again identified as the dominant radical species in degradation of MC-LR in the Fe2+/monopersulfate system. [ABSTRACT FROM AUTHOR]

Pork myofibrillar protein (MP) was selected as the main research material. The Fenton oxidation system was employed to replicate the oxidation conditions of meat items, and curcumin with different concentrations (0, 5, 10, 15, 20 µmol/L) was added to it. Changes in amino acid side chain, secondary structure, tertiary structure and solubility of protein were analyzed. To explore the inhibitory effect of curcumin on the oxidation of pork myofibrillar protein at different concentrations and its specific effect on protein structure. The results showed that curcumin had good free radical scavenging performance and could effectively slow the protein oxidation and structural changes caused by hydroxyl radicals, and this inhibition was proportional to the concentration of curcumin in a specific concentration range (5-20 µmol/ L). Compared with the oxidation group, the curcumin treatment group significantly inhibited the formation of carbonyl groups and the increase of surface hydrophobicity, the curcumin treatment group of 20 µmol/L had the inhibition rates of 2.62% and 51.78%, respectively (P<0.05), can also significantly alleviate the decline of sulfhydryl, free amino and solubility (P<0.05), the inhibition rates were 80.02%, 59.34%, 70.84%, respectively, and the addition of curcumin can promote the MP tertiary structure unfolding, can also alleviate the secondary structure changes caused by hydroxyl radi¬cals. Therefore, curcumin can interact with MP to alleviate its oxidative deterioration and structural changes, and has a good effect on the quality and preservation of meat products. [ABSTRACT FROM AUTHOR]

Tissue inflammation drives the infiltration of innate immune cells that generate reactive species to kill bacteria and recruit adaptive immune cells. Neutrophil activation fosters the release of myeloperoxidase (MPO) enzyme, a heme-containing protein generating hypochlorous acid (HOCl) from hydrogen peroxide (H2O2) and chloride ions. MPO-dependent oxidant formation initiates bioactive oxidation and chlorination products and induces oxidative post-translational modifications (oxPTMs) on proteins and lipid oxidation. Besides HOCl and H2O2, further reactive species such as singlet oxygen and nitric oxide are generated in inflammation, leading to modified proteins, potentially resulting in their altered bioactivity. So far, knowledge about multiple free radical-induced modifications of MPO and its effects on HOCl generation is lacking. To mimic this multi-oxidant microenvironment, human MPO was exposed to several reactive species produced simultaneously via argon plasma operated at body temperature. Several molecular gas admixes were used to modify the reactive species type profiles generated. MPO was investigated by studying its oxPTMs, changes in protein structure, and enzymatic activity. MPO activity was significantly reduced after treatment with all five tested plasma gas conditions. Dynamic light scattering and CD-spectroscopy revealed altered MPO protein morphology indicative of oligomerization. Using mass spectrometry, various oxPTMs, such as +1O, +2O, and +3O, were determined on methionine and cysteine (Cys), and -1H-1N+1O was detected in asparagine (Asp). The modification types identified differed between argon-oxygen and argon-nitrogen plasmas. However, all plasma gas conditions led to the deamidation of Asp and oxidation of Cys residues, suggesting an inactivation of MPO due to oxPTM-mediated conformational changes. [ABSTRACT FROM AUTHOR]

Recently, electrical discharges have been identified as a potentially significant source of the atmosphere's most important oxidant, the hydroxyl radical. Measurements of hydroxyl, the closely related hydroperoxyl radical, and the nitrogen oxides from sparks and subvisible discharges were made in the laboratory under different environmental and electrical conditions representing those found in the troposphere. However, there were still several conditions not yet investigated that could impact hydroxyl and hydroperoxyl production in electrical discharges. In this study, the production of electrically generated hydroxyl and hydroperoxyl (LHOx) and nitrogen oxides (LNOx) was measured under three new conditions not tested previously, including lower pressure, different temperatures, and the presence of cloud droplet‐sized water droplets. In spark discharges, LHOx was mostly independent of pressure, increased with increasing temperature, and was unaffected by the water droplets. LNOx generation was independent of temperature from −10 to 40°C and the presence of water droplets, but increased 1.5‐fold with decreasing pressure. LNOx generation was also found to be sensitive to changes in spark intensity and air flow in the laboratory setup. Increasing temperature also made it more likely that a discharge was visible instead of subvisible, but did not impact LHOx production in subvisible discharges. Even under these new conditions, the laboratory results agree with results of LHOx from a field campaign, demonstrating the relevance of the laboratory experiments to the atmosphere. Plain Language Summary: The hydroxyl radical (OH) reacts with and removes many pollutants in the atmosphere, and electrical discharges, even very weak ones, can make extreme amounts of OH. Previous work has investigated how different pressures and water vapor mixing ratios in the atmosphere could impact production of OH and the closely related hydroperoxyl radical (HO2), but was not able test other important environmental conditions. In this laboratory study, the production of OH and HO2 by sparks was studied at different air temperatures and in the presence of water droplets that mimicked cloud droplets. Under these more realistic conditions the initial OH and HO2 produced by the electrical discharges still agreed well with previous results from a field campaign. Key Points: Electrically generated hydrogen oxides increased with temperature, but were unaffected by cloud droplet‐sized water dropletsProduction of nitrogen oxides in electrical discharges was unaffected by temperature or water dropletsEven under more realistic conditions, the generated hydroxyl is still extreme and similar to the amount measured in a field campaign [ABSTRACT FROM AUTHOR]

Electrochemical amidation of the C(sp2)−H and C(sp3)−H bonds of broad spectrum of arenes toward the direct synthesis of anilides and N‐benzylamides under mild conditions (room temperature, ambient pressure) in the absence of metal catalyst and external oxidizing agents using nitriles RCN (R=Me, Et) as amide source is described. This electrochemical approach features moderate to high yields, a broad scope of arenes with different functional groups and is amenable to gram scale synthesis. The key role of the hydroxyl radical as inductor generated during the oxidation of water and fixed by a spin trap in EPR experiment has been established. [ABSTRACT FROM AUTHOR]

We examined the reaction of hydroxyl radicals (HO•) and sulfate radical anions (SO4•−), which is generated by ionizing radiation in aqueous solutions under anoxic conditions, with an alternating GC doubled-stranded oligodeoxynucleotide (ds-ODN), i.e., the palindromic 5′-d(GCGCGC)-3′. In particular, the optical spectra of the intermediate species and associated kinetic data in the range of ns to ms were obtained via pulse radiolysis. Computational studies by means of density functional theory (DFT) for structural and time-dependent DFT for spectroscopic features were performed on 5′-d(GCGC)-3′. Comprehensively, our results suggest the addition of HO• to the G:C pair moiety, affording the [8-HO-G:C]• detectable adduct. The previous reported spectra of one-electron oxidation of a variety of ds-ODN were assigned to [G(-H+):C]• after deprotonation. Regarding 5′-d(GCGCGC)-3′ ds-ODN, the spectrum at 800 ns has a completely different spectral shape and kinetic behavior. By means of calculations, we assigned the species to [G:C/C:G]•+, in which the electron hole is predicted to be delocalized on the two stacked base pairs. This transient species was further hydrated to afford the [8-HO-G:C]• detectable adduct. These remarkable findings suggest that the double-stranded alternating GC sequences allow for a new type of electron hole stabilization via delocalization over the whole sequence or part of it. [ABSTRACT FROM AUTHOR]

Triclosan (TCS), a broad-spectrum bacteriostatic agent with bactericidal and disinfectant properties, is one of the emerging pollutants of great interest. The electrically activated persulfate-coupled carbon membrane system was studied in this paper. The removal of triclosan achieved 90% within 40 min. Complete degradation can be achieved within 90 min. The electrode was characterized by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The optimal reaction conditions were explored. The catalytic mechanism of the reaction was investigated. It was proved that hydroxyl radicals, sulfate radicals, and singlet oxygen were the main reactive oxygen species in the reaction process by the free radical quenching experiment and electron paramagnetic resonance spectrometer. The degradation path and mechanism of triclosan were investigated. [ABSTRACT FROM AUTHOR]

The generation of hydroxyl radicals from hydrogen peroxide in aqueous solutions containing magnetic nanoparticles (MNPs), hemoglobin (Hb), immunoglobulin G (IgG), and human serum albumin (HSA) was determined. The dependence of the rate of formation of the oxidized product of o-phenylenediamine (o-PDA) on the concentration of MNPs in solution, as well as on the concentration of proteins, was obtained. The peroxidase-like activity of MNPs was shown to decrease in the presence of HSA and IgG, while the addition of Hb to the reaction mixture led to its decrease and increase depending on protein concentration. The obtained effects can be used in the engineering of systems based on MNPs for theranostics (in particular, for suppression of tumor growth) and in predicting the ability of particles to catalyze the generation of reactive oxygen species (ROS) in vivo. [ABSTRACT FROM AUTHOR]

TiO2 is a typical anti‐ultraviolet agent in sunscreen cream, but it suffers from a lack of anti‐oxidant activity for scavenging reactive oxygen species. Other traditional sunscreen ingredients, such as C60 and ferulic acid, have moderate antioxidant and UV protection capabilities, and the products do not provide further UV protection. Herein, titanium hydride (TiH1.97) particles with dual functions of anti‐oxidant and anti‐ultraviolet are presented as an active material to remove the highly oxidizing and harmful hydroxide free radicals from the skin surface. Owing to the active hydrogen in TiH2, it shows great potential to eliminate hydroxyl radicals, and the rate is roughly proportional to the exposed surface area (50% /20 min). Together with the biocompatibility of the in situ formed TiO2, which has a strong ability to absorb ultraviolet light during OH radical scavenging. At the same time, adding titanium hydride to sunscreen also enhances sun protection. The SPF value of sunscreen containing 1% titanium hydride and 20% titanium dioxide can reach 31.8, which exceeds the 20% titanium dioxide (15) by more than twofold. Therefore, titanium hydride with anti‐ultraviolet and antioxidant functions can be regarded as a promising and safe ingredient for sunscreen cream. [ABSTRACT FROM AUTHOR]

Species structure of ammonia (NH 3) micro flames stabilized on a preheated 2-mm diameter tube is investigated using laser-induced fluorescence (LIF) measurements and numerical simulations with detailed reaction mechanisms. Nitric oxide (NO) and hydroxyl (OH) radicals are measured using single-photon absorption laser-induced fluorescence (LIF), while hydrogen atoms (H) are measured using two-photon absorption LIF (TPLIF). NO and OH are measured using nanosecond excitation pulses while both nanosecond and femtosecond methods are employed for TPLIF of H. 1-D and 2-D flame simulations are performed using Cantera and ANSYS FLUENT, separately, and the results are compared with the experimental data. It was observed that experimental H-atom signals increased with increasing equivalence ratio (ϕ), while the model predicted an opposite trend. Compared to the model predicted a rapid drop of OH as a function of ϕ , experimentally measured OH profiles exhibit opposite trends in different height locations of the flame. It is conjectured that the thermal dissociation of NH 3 to generate reactive radicals such as H and OH is enhanced with preheating rich mixtures. Measured NO-LIF signal decreases with increasing ϕ , which agrees with the predicted trend by the simulation. NO reduction in fuel-rich flames is expected to be due to NH i radicals generated from excess NH 3. A negative correlation is observed between NO and H/OH as a function of ϕ , which contradicts with the simulation that shows a positive relationship. This discrepancy implies that the effect of NH 3 thermal dissociation has to be considered in the simulation of rich NH 3 flames. This study helps to fulfill the fundamental knowledge gap of NH 3 dissociation kinetics and the role of reactive intermediates in oxidation and NO formation pathways, hence an important step towards realizing practical combustion devices operating of NH 3 as an energy carrier. [ABSTRACT FROM AUTHOR]

Hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) are potent greenhouse gases regulated under the Montreal Protocol and its amendments. Emission estimates generally use constant atmospheric lifetimes accounting for loss via hydroxyl radical (OH) reactions. However, chemistry‐climate models suggest OH increases after 1980, implying underestimated emissions. Further, HCFCs and HFCs are soluble in seawater and could be destroyed through in situ oceanic microbial activity. These ocean sinks are largely overlooked. Using a coupled atmosphere‐ocean model, we show that increases in modeled OH imply underestimated HCFC and HFC emissions by ∼10% near their respective peak emissions. Our model results also suggest that oceanic processes could lead to up to an additional 10% underestimation in these halocarbon emissions in the 2020s. Ensuring global compliance to the Protocol and accurate knowledge of contributions to global warming from these gases therefore requires understanding of these processes. Plain Language Summary: Man‐made hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) contribute to global warming, prompting worldwide agreement to control the production of these chemicals. It is important to estimate their emissions to ensure global compliance with the agreed phaseout. But correct emission estimation requires knowledge of different loss pathways. One major loss pathway of halocarbons is through chemical reactions with the atmospheric "scrubber" called OH. OH is difficult to measure and usually assumed to be constant with time. But some models suggest OH has increased, which implies increased emissions to match observed abundances. These halocarbons also dissolve into the oceans, where microbes may also metabolize them, but these processes are not included in current emission estimates. We show that if these halocarbons are being consumed in the oceans, this would also lead to an additional underestimation of human emissions. Confidence in the success in the Montreal Protocol and its Kigali amendment to reduce HFCs will therefore require a better understanding of both OH trends and ocean sinks, along with use of HFC and HCFC measurements. Key Points: Increasing OH suggested by Coupled Model Intercomparison Project Phase 6 models can lead to a 5%–7% underestimation in hydrochlorofluorocarbon (HCFC) and hydrofluorocarbon (HFC) emission estimations in 2005If there is significant ocean degradation through microbial activity, HCFC, and HFC emissions could be underestimated by up to 10%Our study suggests an uncertainty in the combined contribution to global warming from HCFCs and HFCs up to 15%–20% in the 2020s [ABSTRACT FROM AUTHOR]

Preparation of CeO2/PbFe12O19 (CO/PFO) heterojunction photocatalysts with the different CO contents as visible‐light photocatalysts were synthesized by a polyacrylamide gel route combined with a low temperature sintering technique. A variety of characterization techniques have been used to confirm that the CO/PFO heterojunction photocatalysts contain only Ce, Pb, Fe and O elements, which also indicates that the special interfacial contact between CO and PFO is formed and there are a large number of oxygen vacancies and interfacial defects in CO/PFO heterojunction photocatalysts. The coupling of CO and PFO enhances the optical absorption coefficients of CO and PFO and slightly decreases the optical band gap (Eg) of the host lattice (PFO). Rhodamine B (RhB), phenol, bisphenol A (BPA) and oxytetracycline hydrochloride (OTC‐HCl) were used as target degradation pollutants to investigate the degradation preference of CO/PFO heterojunction photocatalysts. The degradation percentages of the RhB, Phenol, BPA and OTC‐HCl are 20.35 %, 38.77 %, 18.11 % and 75.32 %, respectively. The results showed that the hydroxyl radical played a dominant role in the degradation of pollutants by the CO/PFO heterojunction photocatalysts and preferred to degrade −C=O and −CONH2. This new idea will provide technical support for cutting functional groups of pollutants purposefully. [ABSTRACT FROM AUTHOR]